Affinity Water And Sodium Hypochlorite

I emailed Affinity water to confirm they used chlorine, which is what the website said but the guy who replied said they use sodium hypochlorite.

Anybody know exactly what impact that would have on my fish if I didnt use water conditioner?

Chlorine itself is a gas and would be quite hard to dissolve in water in a controllable way. Sodium hypochlorite is a solid and it is very easy to add a solid to water in a controllable way.
Sodium hypochlorite decomposes to liberate chlorine. Affinity uses chlorine as their disinfectant, they just use hypochlorite as the safest, most convenient way of adding it.

Sodium Hypochlorite is simply the method of delivering the Chlorine into your water supply. It dissolves and releases free chlorine.

I'd be surprised if that wasn't the most common method employed by most, if not all, UK water companies.

https://en.wikipedia.org/wiki/Water_purification#Chlorine_disinfection

The most common disinfection method involves some form of chlorine or its compounds such as chloramine or chlorine dioxide. Chlorine is a strong oxidant that rapidly kills many harmful micro-organisms. Because chlorine is a toxic gas, there is a danger of a release associated with its use. This problem is avoided by the use of sodium hypochlorite, which is a relatively inexpensive solution that releases free chlorine when dissolved in water. Chlorine solutions can be generated on site by electrolyzing common salt solutions. A solid form, calcium hypochlorite, releases chlorine on contact with water. Handling the solid, however, requires greater routine human contact through opening bags and pouring than the use of gas cylinders or bleach which are more easily automated. The generation of liquid sodium hypochlorite is both inexpensive and safer than the use of gas or solid chlorine.

ps. Sorry for answering when the Q was directed to Sue - I was just at work with a bit of free time and noticed the post.

The sodium will be in the form of the ion Na⁺. Its charge will be balanced by any anion in the water eg Cl^- or NO₃^-